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Add cgroup write_uint() helper method

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Add write_uint() helper method for cgroup subsystems

This helper is analagous to the read_uint() helper method for
reporting u64 values to userspace. It's designed to reduce the amount
of boilerplate requierd for creating new cgroup subsystems.

Signed-off-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Paul Menage 2007-10-18 23:39:33 -07:00 committed by Linus Torvalds
parent bbcb81d091
commit 355e0c48b7
2 changed files with 46 additions and 4 deletions
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8
include/linux/cgroup.h
View file

@ -125,6 +125,14 @@ struct cftype {
ssize_t (*write) (struct cgroup *cont, struct cftype *cft,
struct file *file,
const char __user *buf, size_t nbytes, loff_t *ppos);
/*
* write_uint() is a shortcut for the common case of accepting
* a single integer (as parsed by simple_strtoull) from
* userspace. Use in place of write(); return 0 or error.
*/
int (*write_uint) (struct cgroup *cont, struct cftype *cft, u64 val);
int (*release) (struct inode *inode, struct file *file);
};

42
kernel/cgroup.c
View file

@ -829,6 +829,39 @@ enum cgroup_filetype {
FILE_TASKLIST,
};
static ssize_t cgroup_write_uint(struct cgroup *cont, struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
char buffer[64];
int retval = 0;
u64 val;
char *end;
if (!nbytes)
return -EINVAL;
if (nbytes >= sizeof(buffer))
return -E2BIG;
if (copy_from_user(buffer, userbuf, nbytes))
return -EFAULT;
buffer[nbytes] = 0; /* nul-terminate */
/* strip newline if necessary */
if (nbytes && (buffer[nbytes-1] == '\n'))
buffer[nbytes-1] = 0;
val = simple_strtoull(buffer, &end, 0);
if (*end)
return -EINVAL;
/* Pass to subsystem */
retval = cft->write_uint(cont, cft, val);
if (!retval)
retval = nbytes;
return retval;
}
static ssize_t cgroup_common_file_write(struct cgroup *cont,
struct cftype *cft,
struct file *file,
@ -886,10 +919,11 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
if (!cft)
return -ENODEV;
if (!cft->write)
return -EINVAL;
return cft->write(cont, cft, file, buf, nbytes, ppos);
if (cft->write)
return cft->write(cont, cft, file, buf, nbytes, ppos);
if (cft->write_uint)
return cgroup_write_uint(cont, cft, file, buf, nbytes, ppos);
return -EINVAL;
}
static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft,